The invention relates to a seat having an adjustable seat portion.
One form of seat having an adjustable seat portion comprises a support structure, for example for mounting the seat in its position of use, and, disposed on the support structure, a seat portion or squab which includes a seat plate. The seat plate is adjustable in respect of its angle of inclination relative to the support structure in the longitudinal or fore-and-aft direction of the seat, by means of an adjusting member which is disposed on the seat portion. A seat of that nature is disclosed for example in German laid-open application (DE-OS) No. 32 43 747. When the angle of inclination of the seat plate is adjusted in the fore-and-aft direction of that seat, as indicated above, in the direction of increasing the angle of inclination, then the forward end region of the seat portion is raised and the rearward end region of the seat portion is lowered, relative to the support structure which may be carried for example on an air cushion assembly. As the buttocks of a person using such a seat are supported more particularly on the rearward end section of the seat portion, that is to say, in the vicinity of the backrest portion of the seat, adjustment as indicated above, to increase the angle of inclination of the seat portion, means that the level or height at which the occupant of the seat is supported is reduced, giving a lower sitting position. When the seat is used in a vehicle for example as the seat for the driver, a lower sitting position of that nature can have a seriously adverse effect on the ease with which the driver can operate the vehicle, and thus on the degree of driving safety. It is therefore generally necessary for the occupant of the seat to compensate for the lowered sitting position by operating the air cushion or other assembly on which the support structure of the seat is carried, in order to raise the seat in its entirety. However, that in turn requires additional operation of an adjusting member so that the degree of user-friendliness of such a seat still leaves something to be desired. Furthermore, a seat of that kind only affords a given depth in the seat portion, as measured from the front edge of the seat portion to the rear edge thereof or to the location at which the seat portion meets the backrest portion, with the result that, while the seat may be satisfactory for persons of a given size, other persons of different statures may find that the level of comfort afforded by the seat is not particularly good, in particular due to insufficient support for the thighs where they extend beyond the front edge of the seat.